Four terminal waveguide network



Jan. 6, 1959 N, KO MAN 2,867,773

FOUR TERMINAL WAVEGUIDE NETWORK Filed Aug. 20, 1948 INVENTORMlluznzkllfirm BY I ATTORNEY United States Patent FOUR TERMINALWAVEGUIDE NETWORK Nathaniel I. Korman, Merchantville, N. J., assignor toRadio Corporation of America, a corporation of Delaware ApplicationAugust 20, 1948, Serial No. 45,280

Claims. (Cl. 33311) This invention relates to a four terminal-pairnetwork of the type sometimes known as hybrid couplers.

Four terminal-pair networks having the property that electro-magneticenergy applied to any one terminal-pair will be transferredsubstantially entirely to two of the other terminal-pairs withsubstantially no energy transference to the fourth terminal-pair arewell known to the art. Such networks may he wave guide, coaxial line, oropen line networks. Generally speaking, their properties, advantages,and uses are well known to the art. In particular, my invention isconcerned with hybrid coupler networks employing waveguides of thehollow pipe type. It will be understood that when referring to aterminal pair with reference to a waveguide, the reference is to thewaveguide termination.

Heretofore, the most common type of hybrid coupler network, sometimesknown as the magic tee, is that which employs four rectangularwaveguides having a common junction. Two of these four waveguides may beconsidered as a single waveguide which has a third waveguide making ajunction therewith in the H plane and still another waveguide whichmakes a junction with the first pair of waveguides at the same junctionpoint and in the E plane. The result of this arrangement is that powerfed into any one of the waveguide arms extending from the junction willbe transferred substantially entirely to two of the other arms andsubstantially no energy will be transferred to the fourth arm, ifaccount is not taken of reflected energy. In this common arrangement,the difiiculty is encountered that the orientation of the arms extendingfrom the junction is substantially fixed. Moreover, the division ofpower between the two guide arms which receive power is substantiallyequal. The ratio of power which is transferred to them is substantiallyfixed and cannot be chosen at will.

It is an object of the present invention to provide a four terminal Pairwaveguide network of the hybrid coupler type which is more flexible thanprior types, and more particularly which is more flexible in thearrangement and disposition of the waveguide arms.

It is further an object of the invention to provide such an improved andflexible arrangement in which the arms are rectangular waveguide arms.

It is further an object of the invention to provide a simple arrangementfor a four terminal-pair waveguide network of the hybrid coupler type inwhich the arms may be readily located at a desired distance from eachother.

It is a further object of the invention to provide such an arrangementutilizing rectangular waveguide arms,

These and other objects, advantages and novel features of the inventionwill be apparent from the following description taken in connection withthe accompanying drawing in which:

Figure 1 is a face view of one embodiment of my invention;

Figure 2 is a cross sectional View along the lines 2--2 pt Figure 1;

ice

Figure 3 is a cross sectional view along the lines 3-3 of Figure 1;-

'Figure 4 is a face view of a second embodiment of the invention inwhich a pair of the waveguide terminal arms which are not directlycoupled have a junction separated from the other pair and in which theangular relationship of the paired arms results in other than equalenergy division between arms of the same pair;

Figure 5 is a cross sectional view of the embodiment of Figure 4 alongthe lines 5-5;

Figure 6 is a face view of still other embodiment of invention in whichone pair of uncoupled terminal arms may be angularly related as desiredwith respect to the radial direction of the other pair from the junctionnetwork and a desired division of energy may still result between armsof a pair;

Figure 7 is a cross sectional view of the embodiment of Figure 6 alongthe line 7-7 of Figure 6.

In accordance withmy invention I provide an elliptical waveguide and twopairs of rectangular waveguide terminal arms. Each arm of one pair isoriented with respect to the other arm of the one pair so that energyincident through one arm of the one pair is not coupled to the other armof the one pair through the elliptical waveguide, and the other pair ofarms is coupled to receive substantially all the energy incident throughany one of the arms of the one pair. This is accomplished by excitationof the elliptical waveguide in the TE mode through one of the arms ofone pair, with the waveguide arm of the other one of this one pair beingoriented with respect to the principal vector of that mode so that it isdecoupled from that mode of excitation.

Referring now to the drawings, in which like numerals are used toindicate like parts, and referring more particularly to Figures 1, 2 and3, a circular waveguide 10 has two rectangular waveguide arms 12 and 14extending therefrom and making a junction therewith at substantially thesame point. It is understood that a circular waveguide is a specialinstance of an elliptical waveguide. Waveguide arms 12 and 14 have theiraxes normal to each other and normal to the axis of the circularwaveguide 10. A similar pair of rectangular waveguide arms 16 and '18make a junction with the circular waveguide 10 at a point on the axis ofthe waveguide 10 removed from the point of junction of waveguides 12 and14. Waveguides 12, 14, 16 and 18 have broad and narrow walls and havetheir broad walls oriented parallel to the axis of the circularwaveguide Ill. Circular waveguide 10 is closed at each end to completelyenclose its junctions with the rectangular waveguides by pistons 20 and22 which may be adjusted axially of the circular waveguide for impedancematching and which may comprise choke joints as shown to minimize energyleakage between the pistons and the circular waveguide walls. Matchingdiaphragms may be inserted in the various rectangular waveguides forimpedance matching as will be Well understood by those skilled in theart.

In operation, let it be assumed that energy enters from the terminalwaveguide 12. Such energy in the TE mode in the rectangular waveguidewill excite energy in the TE mode in circular waveguide 10. This mode inthe circular guide is indicated in Figure 3 by the vectors there shown.The principal vector of the TE mode characterizes the orientation andmagnitude of this mode. It will be clear that waveguide 14, which isoriented at right angles to waveguide 12, will not be excited by thisenergy. However, referring to Figure 2, it will be clear that bothwaveguides 16 and 18 will be directly excited by the energy indicated byvector 26. In the example here shown, since waveguides 16 and 18 areeach oriented at a 45 angle, with respect to vector 26', each willreceive half the energy and will be excited as in the comtheir axes atright angles as before.

may be made any desired angle.

3 parative phases indicated by vectors 28. Assuming that the system issubstantially perfectly matched throughout, there will be no reflectedenergy, and the energy represented-by vector 26 will be vectoriallydivided between waveguides 16 and 18 in accordance with the angles'thevector makes withthenormal.tothe axis of therectangular-waveguidesldand18. The distance 1 maybe chosen substantiallyat will affording great flexibility to the arrangement, andease ofconnection with associatedapparatus.

Referring now to Figures 4 and 5, waveguides l2 and l-dare shown havinga junction with waveguide .with Reflecting plates 30 and '32 may be usedto obtain impedance match. Waveguides ldrand 18 similarly form junctionswith waveguide 10, but these junctions are displaced from each otheraxially along waveguide 19 and in this instance, are on opposite sidesofthe junction of waveguides 12 and 14 with waveguide 10.

Theoperation of'thedevice will be apparentfrom what has been saidbefore. Ifany energy is incident through any of the rectangularwaveguides, such energy will not be directly coupled to the rectangularwaveguide paired thereto and'having'its axis'normal to the axisof thewaveguide through which the incident energy enters. Such incident energywill be substantially entirely absorbed by the two rectangularwaveguides of the other pair. The energy absorbed by the'other pair willbe divided therebetween vectorially in accordance with the angles whichthey make with the principal vector of the energy advancing in thecircular waveguide. In this case waveguides 16 and 18, for example, arearranged so that the former receives a major portion of energy fromwaveguide 14, and the latter from waveguide 12, and vice versa.

Still another example of my invention is illustrated .in Figures 6 and7, in which again rectangular waveguides 12, 14, 16 and 18 formjunctions with waveguide 34. Waveguide 34 is circular in cross sectionexcept for a portion 36 thereof which is transformed to be eccentricallyelliptical. The portion 36 is of such a length and has such major andminor axes of the elliptical crosssection that energy advancing throughthe circular waveguide from one side of section 36 in the TE mode andhaving its principal vector oriented in a given direction has itsprincipal vector shifted through angle X, which As Well understood,this;may be accomplished because energy traveling in the ellipticalsection has even and odd modes, in one of which theprincipal vector isalong the major axis and the other of which is along the minor axis ofthe ellipse. .These two modes have differing phase velocities. The

transformation may be adjusted to produce the desired result by means ofa clamp (not shown) exerting pressure against the outside walls ofwaveguide section 36 to a desired degree. Impedance matching deviceshave been omitted, in Figures 4 to 7, because such devices are numerousand well known. Other means are also known to procure the angular shiftof the principal vector of energy in the circular waveguide mentioned incon? nection with Figures 6 and 7.

In the device of Figures 6 and 7, the division of energy between arms 16and 18 incident from, say, arm 12 may be made as desired byappropriately choosing the shift in the direction of the electric vectorof energy in section 36 and the angular relationship of the arms 16 and18 j'with respect-to arm 12. Either section 36 or the angular directionof arms 16 and 18 (the axes of which remain normal to each other) may beindependently adjusted to secure this result. Hence, there is a highlydesirable flexibility in .choosing the relationship of the arms tofacilitate connection with apparatus'of which the waveguidenetwork formsa part.

In practice, it will be be understood that any of the rectangularwaveguides shown in the drawing may be connected to extensions or toother apparatus. Any of the rectangular waveguides may have a resistivematching termination or a crystal and reflective termination, or otherterminations. Such extensions and terminations I have not shown, as theyare peculiar to the device in which my waveguide junction network may beemployed, and do not aid in an understanding of the present invention.

I claim as my invention:

1. A four terminal-pair waveguide network comprising an ellipticalwaveguide having a longitudinal axis and two pairs of waveguide arms,each said arm having a longitudinal axis and having a junction with saidelliptical waveguide, at each said junction the said axes of theelliptical waveguide and the waveguide arm being normal to each other.

2. The device claimed in claim 1, further comprising impedance matchingapparatus to match the impedance of said waveguide arms to the impedanceof said elliptical waveguide at the said junctions.

3. A four terminal-pair waveguide network comprising an ellipticalhollow pipe waveguide having a longitudinal axis and two pairs of hollowpipe waveguide arms, each said arm having a longitudinal axis and havinga .junction with said elliptical waveguide and being adapted forexcitation by electromagnetic energy in a transverse electric modehaving a single principal electric vector normal to the said axisthereof, at each said junction the said axes of the elliptical waveguideand the waveguide arm being normal to each other and said principalvector being oriented normal to the axis of said elliptical waveguide.

4. A four terminal-pair waveguide network comprising an ellipticalhollow pipe waveguide having a longitudinal axis, andtwo pairsofrectangular hollow-pipe waveguide arms, each said rectangular waveguidearm having a longitudinal axis and broad and narrow internal walls andeach having a junction with said elliptical waveguide, at each saidjunction the said axes of the elliptical waveguide and the rectangularwaveguide arm being normal to each other and the broad walls of eachrectangular waveguide arm beingparallel to the said elliptical Waveguideaxis.

5. A four terminal-pair waveguide network comprising an ellipticalhollow pipe waveguide closed on each end and having a longitudinal axis,and two pairs of rectangular hollow pipe waveguide arms, each saidrectangular waveguide arm having a longitudinal axis and broad andnarrow internal walls and each having a junction with said ellipticalwaveguide, at each said junction the said axes of the ellipticalwaveguide and the rectangular waveguide arm being normal to each otherand the broad walls of each rectangular waveguide arm being parallel tothe said elliptical waveguide axis, the waveguide axis of one of saidrectangular waveguide pair being normal to thatofthe other of the samepair.

6. A four terminal-pair hollow pipe waveguide network comprising anelliptical hollow pipe waveguide having a longitudinal axis, andtwopairs of rectangular hollow pipe waveguide arms, each said rectangularwaveguide arm having a longitudinal axis and broad and narrowinternalwalls and each having a junction with said elliptical waveguide, at eachsaid junction the said axes of the elliptical waveguide and therectangular waveguide arm being normal to each other and the broad wallsof each rectangular waveguide arm;being parallel to the said ellipticalwaveguide axis, the waveguide axis of each of said rectangular waveguidepair being normal to that of the other of the same pair.

7. A four terminal-pair waveguide network comprising an ellipticalhollow pipe waveguide having a longitudinal axis, and two pairs ofrectangular hollow pipe waveguide arms, each said rectangular waveguidearm having a longitudinal axis and broad and narrow internal walls andeach having a junction with said elliptical waveguide, at each saidjunction the said axes of the elliptical waveguide and the rectangularwaveguide arm being normal to each other and the broad walls of eachrectangular waveguide armbeing parallel to the said elliptical waveguideaxis, the waveguide axis of each of said rectangular waveguide pairbeing normal to that of the other of the same pair,'the junction of onerectangular waveguide with said elliptical waveguide being displacedalong the said elliptical waveguide axis with respect to the junction ofthe other of the same pair.

8. The network claimed in claim 7, the said junctions of said one .pairof rectangular waveguide arms with the elliptical waveguide displacedfrom each other along said elliptical waveguide axis being on oppositesides of the junction of the other pair of rectangular Waveguides withsaid elliptical waveguide.

9. A four terminal-pair waveguide network comprising a circular hollowpipe waveguide having a longitudinal axis, and two pairs of rectangularhollow pipe waveguide arms, each said rectangular waveguide arm having alongitudinal axis and broad and narrow internal walls and each having ajunction with said circular waveguide, at each said junction the saidaxes of the circular waveguide and the rectangular waveguide arm beingnormal to each other and the broad walls of each rectangular waveguidearm being parallel to the said circular waveguide axis, the waveguideaXisof one of said rectangular waveguide pair being normal to that ofthe other of the same pair.

. 10. A four terminal-pair waveguide network comprising a circularhollow pipe waveguide closed on each end and having a longitudinal axis,and two pairs of rectangular hollow pipe waveguide arms, each saidrectangular waveguide arm having a longitudinal axis and broad andnarrow internal walls and each having a junction with said circularwaveguide, at each said junction the said axes of said circularwaveguide and the rectangular waveguide arm being normal to each otherand the broad walls of each rectangular waveguide arm being parallel tothe said circular waveguide axis, the waveguide axis of one of saidrectangular waveguide pair being normal to that of the other of the samepair.

11. A four terminal-pair waveguide network comprising a circular hollowpipe waveguide closed on each end and having a longitudinal axis, andtwo pairs of rectangular hollow pipe waveguide arms, each saidrectangular waveguide arm having a longitudinal axis and broad andnarrow internal walls and each having a junction with said circularwaveguide, at each said junction the said axes of the circularwaveguide'and the rectangular waveguide arm being normal to each otherand the broad walls of each rectangular waveguide arm being parallel tothe said circular waveguide axis, the waveguide axis of each of saidrectangular waveguide pair being normal to that of the other of the samepair.

12. A four terminal-pair waveguide network comprising a circular hollowpipe waveguide closed on each end and having a longitudinal axis, andtwo pairs of rectangular hollow pipe waveguide arms, each saidrectangular waveguide arm having a longitudinal axis and broad andnarrow walls and each having a junction with said circular waveguide, ateach said junction the said axes or the circular waveguide and therectangular waveguide arm being normal to each other and the broad wallsof each rectangular waveguide arm being parallel to the said circularwaveguide axis, the waveguide axis of each of said rectangular waveguidepair being normal to that of the other of the same pair, the junction ofone rectangular waveguide with said circular waveguide being displacedalong the said circular waveguide axis with respect to the junction ofthe other of the same pair.

13. A four terminal-pair waveguide network, comprising a hollow pipewaveguide having on each end circular closed portions and having alongitudinal axis, and two pairs of rectangular hollow pipe waveguidearms, each said rectangular waveguide arm having a longitudinal axis andbroad and narrow internal walls and each having a junction respectivelywith each said cir cular waveguide end portion, at each said junctionthe said axes of the circular waveguide portion and the rectangularwaveguide arm being normal to each other and the broad walls of eachrectangular waveguide arm being parallel to the circular waveguideportion axis, the waveguide axis of each of said rectangular waveguidepair being normal to that of the other of the same pair, the junctionsof each one of one pair of rectangular waveguides wtih said circularwaveguide portion being at the same point along the said circularportion waveguide axis with respect to the other of the same pair andthe said junctions of one pair being displaced along said hollow pipewaveguide axis with respect to the other pair.

14. The network claimed in claim 13, said hollow pipe waveguide having asection deformed to eccentric ellipticity joining the said circularwaveguide portion.

15. The network claimed in claim 13, said hollow pipe waveguide betweensaid circular waveguide portions having means to rotate the electricvector of electro-magnetic energy passing through said waveguide.

References Cited in the file of this patent UNITED STATES PATENTS2,443,612 Fox June 22, 1948 2,445,895 Tyrrell July 27, 1948 2,458,579'Feldman Jan. 11, 1949

